TS50, Side-tone in frontage

(Volume of listening of handling in telegraphy)

In telegraphy, one needs to hear what one transmits. This "monitoring" is carried out by an oscillator low frequency(1000Hz or 800Hz generally), of which the adjustment of volume is independent. On some transceivers, this adjustment is accessible to the back or sometimes in frontage.

On the TS50, it is necessary to dismount the cap to locate a tiny adjustable resistance "side-tone". Unless planning to often renew the operation, this adjustment is made only once. One could have imagined this adjustable level by a menu....
in the case of a use of the transceiver with more or less of ambient noise, It is interesting to allow an adjustment of the side-tone, more direct and accessible.

On the schematic diagram, one notes that the adjustment "side-tone" VR5 is an adjustable potentiometer of 10kohms.
Which potentiometer in frontage could be used to replace it? (there is not much of it!)
there is one of them, the squelch. that of the TS50 is particular. Its single adjustment in frontage hiding place a double potentiometer. A part is used in CW/SSB/AM and the other out of FM.

We will use part SSB so that once modified, the adjustment "squelch" will function as follows :
In CW/SSB/AM, more function squelch but the adjustment of the "side-tone", in short the listening of handling in transmission.
for the FM mode, the squelch functions normally, knowing that the position of the adjustment will also have an influence on the side-tone (if one makes FM CW).

For this modification which one can see the diagram, VR5 is very accessible and the circuit supporting the potentiometers is easily dismountable.

The degree of disassembling is thus not very important but it is necessary to be very careful. I could not be held responsible for any damage caused on your material following the reading of this text, knowing that the modification is tested and that only a bad handling can be the cause of a failure.

The intervention will proceed as follows :
1- disassembling of the circuit supporting the potentiometers and modification of this one. Few things in fact, two tracks to be crossed, a strap (connection) to realize, two wire to be welded (fine, of electronic wiring and a score of cm). Then reassembly of the circuit of the potentiometers while making pass wire added towards the position vr5.
2- removing of vr5 and welding of wire already connected to the circuit "potentiometers".
A checking before the reassembly of the transceiver and it will be ready.
Duration of the operation : Approximately one hour.

Disassembling

remove the caps.

leave the VFO button by loosening it using a small key six sides. Behind this button are a spring, a plastic fine disc and the ball-ended handle with ovoid grip of the vfo.

detach gradually the external frontage by raising in turn the notches (two in top, two bellow) to release it.
Unscrew the nuts of the potentiometers.

loosen the high side screws of the metal frontage and remove those of bottom.

Remove the loudspeaker by disconnecting its connector, as well as the metal plate on which it is laid out.
Make swivel the frontage. (it is inclined slightly)

Exert a pressure on the axes of the potentiometers while looking inside the frontage. This will make it possible to uncouple of its connector, circuit it supporting the potentiometers. connector CN5 can obstruct a little the exit by the presence of its wires.

Now, you can pass to the modification.

Intervention of potentiometers

The photograph of left is better than a length discourses. Use a cutter to cut the two located tracks. Proceed by successive pressures with the point of the cutter until sparing a small notch in each track. Check with the ohmmeter that continuity is not done any more.

The strap will be produced with some milimeters of wire connecting the two weldings concerned.
For wire welded onto the potentiometers, take care to locate them unless using a pair of wire of different colors.
Modified once, the circuit will resemble the photograph of right-hand side.

Position back the circuit in the frontage. Screw the nuts of the potentiometers. Make walk on the wire until the position of vr5 side tone.

now, made the following test using an ohmmeter :

Put the potentiometer of Squelch in maximum thrust and measure between the ends "1" and "2" of the wire added = 0 ohm (or perhaps a few ohms).

Measure now between the wire "2" and the metal ground of the transceiver = approximately 10 kilo-ohms.
It is the case?, then good news, the modification was correctly made.
Put the external frontage, the buttons.

Let us pass to the continuation, i.e. rv5 (side tone).

Conclusion

remove rv5 while properly cutting its three pins using miniature cutting pliers, without forcing and touching the adjacent components.

Weld the wire "2" at the place where was the cursor of vr5 and the wire "1" on one of the sites remaining, that furthest away from the edge of the circuit. The photograph of right-hand side shows the wires.

And here, it is ready. Replug the loudspeaker and position back its plate support. Push back the frontage in its normal position and tighten its four side screws.
Position back the caps.

Intervention of RV5 Side-tone

The final test shows that there is no more squelch in SSB/CW/AM but that this last always functions on FM. One can now comfortably adjust the level of listening of handling, in emission CW.

It is even possible to put the sound at zero to use interns monitoring of a keyer, for example.